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Author Topic: Lehman Seismograph  (Read 3245 times)
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This project turned out to be very simple compared with my last project(Ultrasonic
Anemometer). There is plenty of detailed information on the web.

I was very interested in:

http://jclahr.com/science/psn/youden/index.html

However I decided to keep it simple and go with:

http://sydney.edu.au/science/uniserve_science/school/Seismograph/menu.html

I followed the mechanical design very closely:



I used the basic LED LDR circuit described at the above site.
His project uses a PC as a continuous logger of the data.
I did not want to allocate a PC for this job.
I used a Arduino 2009 with a SD card as the logger.

I use my library function SDCARDFILES.
This creates text files and appends data to an open file 512 bytes at a time.

Quote
#include <SDCARDFILES.h>

unsigned long now = 0; //the timekeeper
unsigned char buffer[512] ;  // this 512 bytes read from or written to sd card
unsigned int bp = 0; //bufferpointer
unsigned long filesectors = 0; //record of number of sectors in file
const unsigned long maxsectors = 4236; //maximun number of sectors per file(12hrs)

void setup()
{
  pinMode(2, OUTPUT); //error indicator
  digitalWrite(2, LOW);    // set the LED off
  pinMode(3, OUTPUT); //busy indicator
  digitalWrite(3, LOW);    // set the LED off
  Serial.begin(9600);
  int error = SDCARDFILES.createfile();
  if (error !=0)
  digitalWrite(2, HIGH);   // set the LED on for error   
}//end of setup

void loop()
{
  while (millis() - now < 100)
  ; //do nothing until 125 ms has passed
  now += 100;  //update time keeper
  unsigned int sensor = analogRead(A0);
  buffer[bp++] = ((sensor)/1000)%10 + 48; //msb to ascii
  buffer[bp++] = ((sensor)/100)%10 + 48; //next to ascii
  buffer[bp++] = ((sensor)/10)%10 + 48; //next to ascii
  buffer[bp++] = (sensor)%10 + 48; //lsb to ascii
  buffer[bp++] = 32;  //followed by a space
  if(bp == 510)
  {
   digitalWrite(3, HIGH);   // set the LED on for busy   
   buffer[bp++] = 13;  //followed by a CR
   buffer[bp] = 10;  //followed by a LF
   int error = SDCARDFILES.fileappend();  //append one sector to created file
   if (error !=0)
   digitalWrite(2, HIGH);   // set the LED on for error      
  bp = 0;  //reset buffer
  if(++filesectors >= maxsectors)  //have we filled up one file
  {
   int error = SDCARDFILES.createfile();  //move on to the next file
   if (error !=0)
   digitalWrite(2, HIGH);   // set the LED on for error   
   filesectors = 0;  //reset the sector counter
  }//end of we have filled up one file 
  }//end of used buffer 102 samples
  digitalWrite(3, LOW);   // set the LED on for not busy   
}//end of loop


The time that the arduino is reset is noted and used as the time reference.
When the SD card is removed the files are copied to a folder “seismic” on a PC.
This is accessed by a VB program which displays the data:



Simulated plot of an earthquake by a gentle puff of air from 2 meters.
The times are all relative to the start time.

For all the construction details download seismograph_project.zip from:

http://code.google.com/p/mysudoku/downloads/list


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Very cool. 
How sensitive is it?  Can it also detect trains, cars, or people?
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Yes it is very sensitive to extraneous noise.

Also it will have to be in an enclosed box as any air movement will set it off.

I did not have it running during the recent big one in Japan.

I now have it logging data and I expect that it will detect magnitude 6 and above any where in the world
on the line I have set.

I'm on the east coast of Australia and the detector is most sensitive on a line China to New Zealand.

To get full world coverage it is necessary to have two detectors at right angles.
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On our news this morning a magnitude 6.8 on the Burma Thailand border at 8 pm their time.

I checked my data and found:



The onset of the quake sent the detector to full scale.

I checked:

http://www.ga.gov.au/earthquakes/

I found the quake:

M7.0 Myanmar.

UTC time: 24 March 13:55

They have not published their seismograph data yet.

Its nice to see that this design works as advertised.
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Really nice work Carl.
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Thanks novice.

I was really pleased to see a bunch of wood,bolts and nuts(it looks quite odd to me) actually detect an eartquake.
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